摘要
东天山觉罗塔格地区岩浆岩非常发育,以花岗岩类分布最为广泛,对其研究还较为薄弱。本文对觉罗塔格地区主要的花岗岩类岩体系统开展了地质特征研究并进行了同位素精确测年,报道了区内16个主要花岗岩类岩体的锆石LA-ICPMSU-Pb年龄:镜儿泉岩体376.9±3.1Ma、西凤山岩体349.0±3.4Ma、石英滩岩体342±11Ma、长条山岩体337.4±2.8Ma、天目岩体320.2±3.1Ma、百灵山岩体317.7±3.7Ma、白石泉岩体303±18Ma、迪坎岩体288.0±2.5Ma、黄山岩体288±17Ma、白山东岩体284.5±4.5Ma、管道岩体284.1±5.8Ma、红石岩体282.7±4.2Ma、陇东岩体276.2±2.5Ma、多头山岩体271.7±5.5Ma、双岔沟岩体252.4±2.9Ma、土墩岩体246.2±2.6Ma,上述定年结果为研究区岩浆活动与区域构造演化及深部过程的关系研究提供了可靠的年代学支持。结合前人已有的部分年代学成果认为,觉罗塔格地区花岗岩类的形成年龄分布在386～230Ma之间,岩浆活动可分为晚泥盆世(386.5～369.5Ma)、早石炭世(349～330Ma)、晚石炭世-晚二叠世(320～252Ma)、早中三叠世(246～230Ma)等4个阶段。前3个阶段岩浆活动具有持续时间逐渐变长、岩浆活动逐渐加剧的特点,并在第三阶段达到顶峰,而第四阶段岩浆活动则明显变弱。花岗岩类岩浆活动在时空分布上表现为,自哈尔里克-大南湖岛弧带→阿奇山-雅满岛弧带→康古尔-黄山韧性剪切带,岩体侵位由早到晚;自研究区东部→中西部→沿韧性剪切带,岩体侵位由老到新。结合区域构造演化研究成果认为,觉罗塔格地区花岗质岩浆活动与区域构造演化具有很强的耦合关系,花岗岩类在前碰撞阶段、主碰撞阶段、后碰撞阶段、板内阶段等4个构造演化阶段均有发育,与花岗岩类在时间分布上的4个阶段完全对应,其中尤以后碰撞构造演化阶段花岗岩类的分布最广泛、岩浆活动最强烈。觉罗塔格地区与4个阶段花岗岩类有关的成矿作用由早到晚具有无明显矿化→斑岩型铜矿、火山岩型铁矿→韧性剪切带型金矿、夕卡岩型银(铜)矿→斑岩-石英脉型钼矿的演化特点,其中以对应于主碰撞阶段的斑岩型铜矿和后碰撞阶段的韧性剪切带型金矿最为发育。本文系统阐述了东天山觉罗塔格地区中酸性岩体的时空格架、与区域构造演化的耦合、与成矿作用的关系,为北疆地区晚古生代特别是后碰撞背景下的岩浆演化及其成矿关系的研究提供了有力支持。
There distributes a lot of magmatic rocks,most of them are granitic rocks in the Jueluotag area,eastern Tisnashan, Xinjiang.The previous research on these granitic intrusions is inadequate.In this work,the geological characteristics of the major granitic plutons in the area have been investigated,and their isotopic ages are systematically dated through the zircon LA-ICPMS U-Pb method.The precise age data of the 16 granitic plutons are as follows;Jingerquan pluton 376.9±3.1Ma,Xifengshan pluton 349.0±3.4Ma,Shiyingtan pluton 342±11 Ma,Changtiaoshan pluton 337.4±2.8Ma,Tianmu pluton 320.2±3.1Ma,Bailingshan pluton 317.7±3.7Ma,Baishiquan pluton 303±18Ma,Dikan pluton 288.0±2.5Ma,Huangshan pluton 288±17Ma,Baishandong pluton 303±18Ma,Guandao pluton 284.1±5.8Ma,Hongshi pluton 282.7±4.2Ma,Longdong pluton 276.2±2.5Ma,Duotoushan pluton 271.7±5.5Ma,Shuangchagou pluton 252.4±2.9Ma and Tudun pluton 246.2±2.6Ma.These age data provide important information and bases for the investigations of genetic relation between the magmatic activities and the tectonic evolution in this area,as well as with the deep dynamic processes.Combined with some known chronological data of the granitic plutons in this area from other workers, this article has constrained the intrusion and crystallization time framework of the granitic plutons in Jueluotage to be between 386Ma and 230Ma.The granitoid magmatic activity can be divided into four stages,which are the Late Devonian stage(386.5～369.5Ma), the Early Carboniferous stage(349～330Ma),the Late Carboniferous to Late Permian stage(320～252Ma) and the Middle Triassic stage(246～230Ma).The early three stages of the granitoid activities tend to be lasting longer and more intense from the first to the third stage,and the third stage reached the peak in the area,and the magmatic activities in the forth stage became weak and scattered. The intrusion ages of the granitic plutons became younger from Haerlike-Dannanhu island arc belt,to Aqishan-Yamansu island arc belt,then to Kangguer-Huangshan ductile shear zone,and the granitoids also showed a youngering trend from the east of study area to the mid-west of study area,then to the ductile shear zone.Based on the post-collision theory and the results for the orogeny of Central Asia and northern Xinjiang,there display affinitive relationship between the granitoid magmatic activity and the tectonic evolution in the study area.This article further proposes a model for the evolution of granitoids in Jueluotage area;The magmatic activity in this area had undergone through the pre-collisional stage,the collisional stage,the post- collisional stage and the within-plate stage,which completely correspond with the four temporal stages of granitoids,and most of granitoids formed in the post- collisional stage.In jueluotage area,the mineralization with the four stages granitoids started from no obvious mineralization,to the porphyry copper deposits and volcanic iron deposits,then to the ductile shear zone type gold deposits and skarn-type Ag(Cu) deposits,lastly to the porphyry quartz veins deposits.The porphyry copper deposits controlled by the collisional geodynamic process and the ductile shear zone type gold deposits controlled by the post-collisional geodynamic process are the main mineralization types with granitoids in the study area This work systematically expatiated the granitoids in Jueluotag area with the characters of temporal and spatial distribution, the relationships with the tectonic evolution and mineralization,which supplied a solid foundation for further research on the magmatic evolution and mineralization in Late Paleozoic,especially in the post- collisional stage in northern Xinjiang.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2010年第2期478-502,共25页
Acta Petrologica Sinica
基金
国家重点基础研究发展规划项目(2007CB411304
2001CB409800)
国家自然科学基金项目(40772057)
新世纪优秀人才支持计划项目
中国地质大学地质过程与矿产资源国家重点实验室基金项目(GPMR200706)
安徽省优秀青年科技基金项目(08040106907
04045063)联合资助
